The present invention relates to photographic processes in general and, more particularly, to a photographic process in which multiple images are transferred to a single image receiving surface.
The use of diffusion transfer development processes is well known in the photographic art. Perhaps the most obvious example of the use of a DTR process is in the field of "instant" photography. "Instant" photography was developed and commercially exploited by the Polaroid Corporation of Cambridge, Massachusetts. The general photographic process employed in "instant" photography was described by Polaroid Corporation's founder, Dr. Edwin H. Land; in an article entitled "A New One-Step Photograhic Process" published in the Journal of the Optical Society of America, Vol. 37, No. 2, February 1947, at Pages 61-77. The United States patent literature is replete with Polaroid Corporation's patents which describe and claim various processes, equipments and materials for "instant" photography. Representative examples include the following U.S. Pat. Nos. 2,500,421; 2,543,181 and 3,345,161, (processes); 2,774,667 and 3,345,166 (negative materials); 2,698,237; 2,698,245; 2,774,667 and 3,345,166 (processing chemicals); 2,698,237; 2,698,238, 2,698,245; 2,774,667 and 2,823,122 (receiver sheets).
In recent years considerable interest has been shown in the idea of using photographic processes to produce electrically conductive patterns and components in which the photosensitive material itself forms a part of the pattern or component. This is in contrast to the conventional photoresist techniques for producing copper-clad printed circuit boards in which the current carrying copper itself is not photosensitive.
Various proposals have been suggested to use the exposed silver in a photographically developed negative as a current carrying element. See of example U.S. Pat. Nos. 3,647,456 (IBM) and 3,551,149 (Polaroid). The amount of silver in the exposed and developed areas of the negatives was considered insufficient to achieve the required conductivity for circuit applications such as, printed circuit boards. A number of processes to increase the conductivity of the photographically formed silver patterns have been described in the patent literature, e.g. intensification of the exposed areas, U.S. Pat. Nos 3,615,483 (U.S. Phillips) and 3,822,128 (Horizons, Inc.); diffusion transfer reversal 3,464,822 (DuPont); and D.T.R. with intensification 3,822,127 (Fugi) and 3,033,765 (Kodak).
The photographic processes described in the above-listed patents were relatively complicated and achieved generally marginal results in terms of the requisite electrical conductivity of the photographically produced silver pattern.
It is accordingly a general object of the present invention to provide a photographic process and article in which multiple images of unexposed and developed photosensitive material are formed on a single receiving surface.
It is a specific object of the invention to provide a photographic process for producing electrically conductive patterns and components in which the photosensitive materials, itself, forms part of te patterns and components.
It is still another object of the invention to photographically produce electrically conductive patterns and components using a diffusion transfer development process.
It is a feature of the invention and that the novel process thereof can be carried out with conventional apparatus, photosensitive materials and processing chemistry.
It is another feature of the invention that the novel photographic process can be varied to obtain predetermined electrical resistivities in the photographically formed electrical patterns and components.